The ten indicators of temperature have been compiled by the Met Office Hadley Centre, drawing upon the work of over 100 scientists from over 20 institutions. They provide, in one place, a snapshot of our world and spell out a single conclusion that the climate is unequivocally warming.

Relying on data from multiple sources, each indicator proved consistent with a warming world. Seven indicators are rising: air temperature over land, sea-surface temperature, marine air temperature, sea level, ocean heat, humidity, and tropospheric temperature in the “active-weather” layer of the atmosphere closest to the earth’s surface. Three indicators are declining: Arctic sea ice, glaciers and spring snow cover in the northern hemisphere.

Observations that are all increasing, consistent with a warming world

Observations that are all decreasing, consistent with a warming world.

Dr. Peter Stott contributor to the report and Head of Climate Monitoring and Attribution at the Met Office Hadley Centre said: “Despite the variability caused by short-term changes, the analysis conducted for this report illustrates why we are so confident the world is warming.

“When we look at air temperature and other indicators of climate, we see highs and lows in the data from year to year because of natural variability. Understanding climate change requires looking at the longer-term record. When we follow decade-to-decade trends using different data sets and independent analyses from around the world, we see clear and unmistakable signs of a warming world.”

While year-to-year changes in temperature often reflect natural climatic variations such as El Niño/La Niña events, changes in average temperature from decade-to-decade reveal long-term trends such as global warming. Each of the last three decades has been much warmer than the decade before. At the time, the 1980s was the hottest decade on record. In the 1990s, every year was warmer than the average of the previous decade. The 2000s were warmer still.

The 2009 State of the Climate is published as a special supplement to the Bulletin of the American Meteorological Society and is edited by D.S. Arndt, M.O. Baringer, and M.R. Johnson. The full report and an online media packet with graphics is available at: http://www.ncdc.noaa.gov/bams-state-of-the-climate.